This invention relates to a new cut for a precious or semi-precious jewel. Cut in accordance with the present invention, the jewel displays enhanced overall brilliance. Specifically, by providing two or more culets to a gem, along with a plurality of ordinary facets, and having at least one additional facet extending from the end of the jewel to the extra culet, at the preferred 41.degree. angle (for diamonds) the brilliance of the gem is enhanced. In addition, the "bow-tie"of darkness, which ordinarily appears in brilliant cut gems having a single culet is reduced in that the gem, cut with two or more culets and two or more additional facets at 41.degree., distributes the bow-tie "darkness" among the other facets. In this manner, the overall brilliance of the stone is apparently enhanced.
A jewel's brilliancy is generally divided into two types, namely internal and external. External brilliance is often referred to as the luster of the diamond. When a ray of light strikes the table or top surface, it is split into two partial light rays, one penetrating into the surface of the gem and the other reflecting off the stone. The angle of reflection is generally equal to the angle of incidence of light, a consequence of the index of refraction and mirror aspects of a diamond, when appropriately cut and polished. Internal brilliance, on the other hand, is caused by the light rays which enter generally through the crown of the gem and its associated table area. These light rays are refracted, internally of the gem, and then reflected by the base facets back through the crown and table area as undispersed light. The refracted index for a diamond is 2.42. This allows for a small critical angle. This angle, in turn, allows for a ray of light striking the base facet to be totally reflected out through the top, crown and table area, of the stone. This is only possible if proportions are kept within the critical angle.
Precious gems, it is well known, are cut with a plurality of facets at predetermined angles. The facets and angles are intended to enhance the light reflecting and refracting aspects of the gem. Studies indicate that a gem's brilliance can be significantly enhanced when the facets are made at angles which take into account the gem's index of refraction. Consistent with standard and conventional gem-cutting techniques, diamonds, rubies, sapphires and emeralds have been traditionally cut with a single culet and a plurality of facet faces beneath the girdle of the stone which are directed toward the culet. This cut has, in the past, provided maximum light refraction within the gem with maximum light emanating through the table of the gem. High brilliance is a very important factor in a gem's value.
The present invention contemplates the cutting of two or more culets on the bottom of a precious stone, along an axis of symmetry. This allows the provision of at least two additional, end base facets to be cut at the 41.degree. angle, the preferred angle for diamond refraction. This angle has been determined to be the preferred angle in diamond cutting for base facets. This, it has been determined, provides for maximum brilliance of the gem. The 41.degree. angle for the additional base facets provided by the cutting of additional culets, consistent with the present invention, reduces the bow-tie "dullness" or darkness at the sides of the diamond and, further, distributes the gem's brilliance more uniformly around the entirety of the stone. Furthermore, the brilliance of the gem can be enhanced by the use of extra side split facets. The effect is enhanced further by additional base end split facets.